MAX1908ETI+ Maxim Integrated Products, MAX1908ETI+ Datasheet - Page 24

• Manufacturer Part Number: MAX1908ETI+
• Description: IC CHARGER BATTERY 28-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX1908ETI+

• Function: Charge Management
• Battery Type: Multi-Chemistry
• Voltage - Supply: 8 V ~ 28 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-WFQFN Exposed Pad
• Product: Charge Management
• Operating Supply Voltage: 2.5 V to 3.6 V
• Supply Current: 400 uA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Charge Safety Timers: Yes
• Mounting Style: SMD/SMT
• Temperature Monitoring: No
• Uvlo Start Threshold: 7 V
• Uvlo Stop Threshold: 7.85 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The crossover frequency is given by:
The CCI loop dominant compensation pole:
where the GMI amplifier output impedance, R
10MΩ.
Low-Cost Multichemistry Battery Chargers
Figure 7. CCI Loop Diagram
24
______________________________________________________________________________________
CCI
C
CI
f
P CI
100
-20
-40
-60
80
60
40
20
_
0
R
OGMI
f
0.1
CO CI
=
GM
_
2π
OUT
GMI
1
R
=
OGMI
10
2π
vs. FREQUENCY
CCI LOOP GAIN
GMI
FREQUENCY (Hz)
1
C
100
ICTL
CI
×
CSIP
C
CI
1k
RS2
CSI
10k
CSIN
100k
OGMI
1M
=
To calculate the CCI loop compensation pole, C
GMI = 1µA/mV
GM
R
f = 400kHz
Choose crossover frequency f
MAX1908/MAX8724/MAX8765/MAX8765A switching
frequency:
Solving for C
To be conservative, set C
crossover frequency at:
The compensation pole, f
Compensation of the CCS loop depends on the parame-
ters and components shown in Figure 9. C
loop compensation capacitor. A
the current-sense amplifier. RS1 is the input current-
sense resistor, RS1 = 10mΩ. R
output impedance of the GMS amplifier ≥ 10MΩ. GMS is
OGMI
-105
OUT
-15
-30
-45
-60
-75
-90
0
0.1
= 10MΩ
= 3.33A/V
1
CI
f
P CI
_
, C
10
f
f
CO CI
CCI LOOP PHASE
CO CI
vs. FREQUENCY
CI
FREQUENCY (Hz)
=
= 2nF.
_
100
_
2
π
R
=
OGMI
=
1k
P_CI
GMI
2 10
2
GMI
π
π
GMI
CI
C
10k
is set at:
×
CCS Loop Definitions
CI
nF
C
= 10nF, which sets the
CSS
OGMS
100k
CI
CO_CI
=
=
80
16
=
is the internal gain of
1M
kHz
0 0016
kHz
.
is the equivalent
to be 1/5th the
CS
Hz
is the CCS
CI
: